Dataset Information

Functional analysis of the osteoarthritis susceptibility-associated GDF5 regulatory polymorphism.

ABSTRACT: OBJECTIVE:Single-nucleotide polymorphism (SNP) rs143383 (T to C) in the 5'-untranslated region (5'-UTR) of GDF5 has recently been reported to be associated with osteoarthritis (OA) susceptibility, with lower expression of the risk-associated T allele observed in vitro and in vivo. The in vivo studies were performed on cartilage tissue from OA patients. The present study was undertaken to expand the analysis of the effect of this SNP on GDF5 allelic expression to more joint tissue types, to investigate for cis and trans factors that interact with the SNP, and to examine novel cis-acting GDF5 regulatory polymorphisms. METHODS:Tissue samples were collected from OA patients undergoing joint replacement of the hip or knee. Nucleic acid was extracted, and, using rs143383 and an assay that discriminates and quantifies allelic expression, the relative amount of GDF5 expression from the T and C alleles was measured. Additional common variants in the GDF5 transcript sequence were interrogated as potential regulatory elements using allelic expression and luciferase reporter assays, and electrophoretic mobility shift assays were used to search for trans factors binding to rs143383. RESULTS:We observed a consistent allelic expression imbalance of GDF5 in all tissues tested, implying that the functional effect mediated by rs143383 on GDF5 expression is joint-wide. We identified a second polymorphism, located in the 3'-UTR of GDF5, that influenced allelic expression of the gene independent of rs143383. Finally, we observed differential binding of deformed epidermal autoregulatory factor 1 (DEAF-1) to the 2 alleles of rs143383. CONCLUSION:These findings show that the OA susceptibility mediated by polymorphism in GDF5 is not restricted to cartilage, emphasizing the need to consider the disease as involving the whole joint. The existence of an additional cis-acting regulatory polymorphism highlights the complexity of the regulation of expression of this important OA susceptibility locus. DEAF-1 is a trans-acting factor that merits further investigation as a potential tool for modulating GDF5 expression.

SUBMITTER: Egli RJ

PROVIDER: S-EPMC6860363 | biostudies-literature | 2009 Jul

REPOSITORIES: biostudies-literature

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Functional analysis of the osteoarthritis susceptibility-associated GDF5 regulatory polymorphism.

Egli Rainer J RJ Southam Lorraine L Wilkins James M JM Lorenzen Inken I Pombo-Suarez Manuel M Gonzalez Antonio A Carr Andrew A Chapman Kay K Loughlin John J

Arthritis and rheumatism 20090701 7

<h4>Objective</h4>Single-nucleotide polymorphism (SNP) rs143383 (T to C) in the 5'-untranslated region (5'-UTR) of GDF5 has recently been reported to be associated with osteoarthritis (OA) susceptibility, with lower expression of the risk-associated T allele observed in vitro and in vivo. The in vivo studies were performed on cartilage tissue from OA patients. The present study was undertaken to expand the analysis of the effect of this SNP on GDF5 allelic expression to more joint tissue types, ...[more]

PMID: 19565498

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Project description:A genetic deficit mediated by SNP rs143383 that leads to reduced expression of GDF5 is strongly associated with large-joint osteoarthritis. We speculated that this deficit could be attenuated by the application of exogenous GDF5 protein and as a first step we have assessed what effect such application has on primary osteoarthritis chondrocyte gene expression. Chondrocytes harvested from cartilage of osteoarthritic patients who had undergone joint replacement were cultured with wildtype recombinant mouse and human GDF5 protein. We also studied variants of GDF5, one that has a higher affinity for the receptor BMPR-IA and one that is insensitive to the GDF5 antagonist noggin. As a positive control, chondrocytes were treated with TGF-β1. Chondrocytes were cultured in monolayer and micromass and the expression of genes coding for catabolic and anabolic proteins of cartilage were measured by quantitative PCR. The expression of the GDF5 receptor genes and the presence of their protein products was confirmed and the ability of GDF5 signal to translocate to the nucleus was demonstrated by the activation of a luciferase reporter construct. The capacity of GDF5 to elicit an intracellular signal in chondrocytes was demonstrated by the phosphorylation of intracellular Smads. Chondrocytes cultured with TGF-β1 demonstrated a consistent down regulation of MMP1, MMP13 and a consistent upregulation of TIMP1 and COL2A1 with both culture techniques. In contrast, chondrocytes cultured with wildtype GDF5, or its variants, did not show any consistent response, irrespective of the culture technique used. Our results show that osteoarthritis chondrocytes do not respond in a predictable manner to culture with exogenous GDF5. This may be a cause or a consequence of the osteoarthritis disease process and will need to be surmounted if treatment with exogenous GDF5 is to be advanced as a potential means to overcome the genetic deficit conferring osteoarthritis susceptibility at this gene.

Project description:BackgroundThe arcOGEN genome-wide association study reported the rs9350591 C/T single nucleotide polymorphism (SNP) as marking a region on chromosome 6q14.1 that is associated with hip osteoarthritis (OA) in Europeans, with an odds ratio (OR) of 1.18 and a p-value of 2.42 × 10(-9). rs9350591 is an intergenic SNP surrounded by seven genes within 1 Mb. Six of the genes are expressed in cartilage. We sought to characterise this signal to assess whether the association of rs9350591 with OA is mediated by modulating gene expression.MethodsTotal RNA was extracted from hip or knee cartilage of 161 OA patients and from hip cartilage of 29 non-OA patients who had undergone hip replacements as a result of neck-of-femur (NOF) fractures. We used quantitative PCR (qPCR) to measure overall gene expression, and pyrosequencing to assess allelic expression of the genes. A mesenchymal stem cell (MSC) differentiation model was used to assess gene expression during chondrogenesis.ResultsWe identified a significant decrease in the expression of SENP6 (p = 0.005) and MYO6 (p = 0.026) in OA hip cartilage relative to the non-OA hip control cartilage. However, we found no evidence for a correlation between gene expression and rs9350591 genotype for any of the six genes. In addition, we identified expression quantitative trait loci (eQTLs) operating on COL12A1, TMEM30A, SENP6 and MYO6, although these were not relevant to the OA associated signal. Finally, all genes were dynamically expressed during chondrogenesis.ConclusionsThe regulation of gene expression at this locus is complex, highlighted by the down-regulation of SENP6 and MYO6 in OA hip cartilage and by eQTLs operating on four of the genes at the locus. However, modulation of gene expression in the end-stage OA cartilage that we have investigated is not the mechanism by which this association signal is operating. As implied by the dynamic patterns of gene expression throughout chondrogenesis, the association signal marked by rs9350591 could instead be exerting its effects during joint development.

Dataset Information

Functional analysis of the osteoarthritis susceptibility-associated GDF5 regulatory polymorphism.

Publications

Functional analysis of the osteoarthritis susceptibility-associated GDF5 regulatory polymorphism.

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